a) Field of the Invention
The invention relates to novel gelloid compositions, methods of making gelloid compositions, methods of covering a substrate and providing an insulative, conductive or stress grading layer of a gelloid composition and gelloid compositions with an electrical device.
b) Background Information
A wide variety of substrates require protection from adverse environmental conditions, including moisture, insects, dirt, plant life and corrosion deposits. In some cases, especially when electrical substrates, such as cable joints, are to be protected, it is desirable to provide a removable protective cover over the substrate, so that it is possible easily to reenter and work on the sealed substrate. A variety of materials have been proposed for this use. In UK published application No. 2,133,026 a sealant having a certain cone penetration and elongation is disclosed. The particular embodiment described in that application utilizes a polyurethane composition containing olefinic unsaturation. These compositions have been found to have relatively low heat stability which has tended to limit their use when they are subjected to elevated temperatures for extended periods of time. Certain electrical devices, particularly those operating at high voltage, e.g. above about 1 kV, may be subjected to operating temperatures of 90.degree. C. or higher from time to time. A sealant composition capable of withstanding such temperatures for an extended period would be advantageous.
In U.S. Patent No. 3,425,967, silicone compositions are described. These silicone compositions show thermal insulating properties and are useful with electrical devices. The silicone compositions, however, have a relatively high water permeability and tend to have low adhesion properties to common solid dielectric materials such as crosslinked polyethylene.
In U.S. Patent No. 3,935,893, a sealant layer is made of a quantity of high and low molecular weight butyl rubber, a liquid polybutylene tackifier, a partially hydrogenated block copolymer of styrene and a conjugated diene, carbon black and curing agents for the butyl rubber. The sealant is designed to heal punctures in vehicle tires and exhibits both adhesive and cohesive second degree blocking.